Process of conditioning cellulosic fiber for the manufacture of rayon



Patented Apr. 15, 193 0:

UNITED STATES rnocnssor oonnrrron'me cnnnunosrc FIBER run run nmfirsorm or :luxon no Drawing. Application filed July 1a, 1926,

This invention relates to the conditioning of cellulosic fiber for the manufacture of rayon by the viscose process, and has for its object to make available as a satisfactory raw material for rayon manufacture, without change of present equipment, certain cellulosic fibers with which difiiculty is encoun-' g a suitable period and are finally converted into viscose or cellulose xanthate by treatment with carbon bisulphide. i

The handling and treatment of pulp while in sheet form with a caustic soda solution are simple andeconomical, but it is desirable that the pulp be retained in sheet form during treatment, to permit it to be removed and finally pressed as such, as this facilitates handling of the material. The usual commercial unbeaten sulphite pulp, cotton fiber,

' or refined sulphite pulp high in alpha cellulose content, when submerged in caustic soda solution in the'form of sheets, retains such form satisfactorily and nodifiiculty 15 encountered in this treatment, but nevertheless such raw material, due to inequality of fiber size and other factors, requires a prolonged depolymerization reaction period for comlete conversion of its largest fibers 1n to a1- kali cellulose, and results in a non-umform reaction and an undesirabledegradation of the shortest fibers, which undergofurther changes in the period required for such complete conversion of the largest. fibers. On the other hand, when sheets of unbeaten pulp are submer ed in a caustic soda solut on, they become'so and punky, and soon disintegrate. This leads to inoonvemenceand PATENT: ormcr.

\ I GEORGE A. RICHTER, 0F BERLIN, NEW OI I BERLINQ NEW HAMPSHIRE, A CORPORATION OF MAINE ASSIGNOR '10 BROWN COHIANY Serial No. 122,271. Benewed June 28, 1929.

diificulty inremoving the pulp from the bath and its subsequent handling.

I have found that if kraft or soda orother pulp is first beaten to a material extent and then formed into sheets, disintegration will not take place when such sheets' are submerged in a caustic soda solution preparatory to conversion into viscose and a much more uniformly treated product, which depolymerizes more uniformly and which gives a higher yield of a better quality viscose, is realized. In accordance with this finding, therefore, the-pulp is beaten or hydrated to a moderate or greater slowness, and is then formed .into waterleaf sheet or paper on a paper machine. The beaten, sheeted pulp may be soaked in a caustic soda solution of proper concentration until it has absorbed suflicient caustic soda for'subsequent treatment without undergoing disintegration, and may be removed and subjected to pressure while in sheet form forlthe removalof excess solution. After ageing the sheeted pulp under the proper conditions for the necessary period, itmay be shredded into fiber flocks and then xanthated.

It is my opinion that when an'unbeaten kraft sheet is treated with a caustic soda solution prior to xanthation, suflicient ligneous matter and pentosan is dissolved and removed from the interfelted fibers to cause a general softening and loosening of the fibers and con sequent disintegration of the sheet. This disintegrating action on kraft sheets may be slowness prior to s eeting, however, a

sufiiciently tenacious bondingkor cementing together of the interfelted fi rs is efiected to retard or resist disintegrating action in a strong caustic soda solution."

In instances where pulp of other variety,

such as soda pulp derived from spruce, ine,

birch or poplar, or kraft or soda pulps w ch have been bleached, or refined by further alkaline. treatment, as described in my apptreated in sheet plication Serial No. 73,193, filed December 4, 1925, under oes disintegration when orm with a caustic solution prior to xanthation, such disintegration is prevented, in accordance with the present invention, by beatin the pulp to a sufiicient extent prior to its s eeting and subsequent treatment with caustic soda solution.

In the treatment of pulp such as herein referred to for xanthation purposes, it is found that a substantial beating of the pulp and its formation into waterleaf paper produces other highly desirable results. Thus, beating effects a greater uniformity of fiber size an a greater uniformity of fiber distribution, and consequently a sheet of paper of uniform thickness and texture is secured. As a result, a more uniform impregnation of the fibers.with caustic soda in the first step of the viscose conversion process is, effected. Similarly, in ageing or seasoning the sheets, a more uniform de olymerization of the fibers is effected, an when such sheets are shredded, more uniform fiber flocks are produced which xanthate more uniformly and in a s orter period of time without leaving such a high proportion of unxanthated fibers or so-called whiskers, which are liable to clog the orifices of the spinnerets and which must, therefore, be filtered out.

I do not herein claim the subject ,matter of pftent application, Serial No. 97,998, filed arch 27, 1926, by Milton 0. Schur, Royal H. Rasch, and myself, wherein the advantages of beating cellulose fiber prior to nitration are disclosed, or the subject matter of its continuation application, Serial No. 140,674, filed October 9, 1926. Nor do I herein claim broadly the subject matter of my application, Serial No. 194,506, filed May 26, 1927, which discloses the advantages of first preparing a waterleaf paper from cellulose fiber, and then xanthating such pa er. Nor do I herein claim broadly the su ject matter of my application, Serial No. 196,135, filed June 2, 1927, which discloses the advantages of materially reducing or pulverizing cellulose fiber prior to conversion into derivatives such as cellulose xanthate.

Having thus described this invention, it

should be obvious that it is susceptible of various changes and modifications without departing from its spirit or scope as defined by the appended claims.

What claim is: v

1. A which comdpsrises beating a punlp w ch undergoes integration if so ed in unbeaten sheet form in a solution of caustic soda, sheeting the beaten pulp, treat-- 2. A process which comprises beating pulp ,derived from alkaline digestion, sheeting the pulp, treatingthe sheeted pulp with a soluing the pulp into a waterleaf paper, treating the paper with caustic soda solution, and converting the treated paper into viscose.

. 5. A process which comprises,-'-beating cellulose pulp, converting the beaten pulp into sheet form, immersing the sheet in canstic soda solution shredding the sheet, and xanthating the shreds.

In testimony whereof I have afiixed my signature.

GEORGE A. RICHTER. 

